Antimicrobial peptides (AMPs) expressed by epithelial and immune cells are largely described for the defense against invading microorganisms. Recently, their immunomodulatory functions have been ...highlighted in various contexts. However how AMPs expressed by non-immune cells might influence autoimmune responses in peripheral tissues, such as the pancreas, is unknown. Here, we found that insulin-secreting β-cells produced the cathelicidin related antimicrobial peptide (CRAMP) and that this production was defective in non-obese diabetic (NOD) mice. CRAMP administrated to prediabetic NOD mice induced regulatory immune cells in the pancreatic islets, dampening the incidence of autoimmune diabetes. Additional investigation revealed that the production of CRAMP by β-cells was controlled by short-chain fatty acids produced by the gut microbiota. Accordingly, gut microbiota manipulations in NOD mice modulated CRAMP production and inflammation in the pancreatic islets, revealing that the gut microbiota directly shape the pancreatic immune environment and autoimmune diabetes development.
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•Pancreatic β-cells express the cathelicidin-related antimicrobial peptide (CRAMP)•CRAMP is protective in the adult NOD mice, a model for type 1 diabetes•CRAMP converts inflammatory into regulatory immune cells in the pancreas•The gut microbiota via short-chain fatty acids governs CRAMP production by β-cells
It is unclear to what extent antimicrobial peptides expressed by epithelial cells influence immunity in peripheral tissues. Diana and colleagues show that the gut microbiota via short-chain fatty acids promote antimicrobial peptide CRAMP expression in pancreatic α- and β-cells, which protects against autoimmune diabetes in NOD mice
Review on endogenous antimicrobial peptide induction by (phenyl)butyrate and vitamin D3 as a new anti‐infective strategy.
As traditional antibiotics gradually become inefficient, there is a high ...demand for development of anti‐infectives with a mechanism of action that is different from existing antibiotics. Current antibiotics target the pathogen directly, thereby contributing to the selection of multidrug‐resistant bacterial strains. AMPs, such as the human cathelicidin LL‐37, are small cationic peptides that are part of host defense. They eliminate microbes through diverse mechanisms, thereby contributing to resolution of infections and maintenance of epithelial barrier function. The multiplicity of these mechanisms of action might be a key to restrict the development of resistant bacterial strains. The discovery of LL‐37‐inducing components, such as butyrate and vitamin D3, has opened new avenues to prevent or treat infections. Butyrate and vitamin D3 are potent inducers of LL‐37 but in addition, have many other effects on host immunity. Here, we summarize current data on the effects that LL‐37 and its inducers display on the innate immune response and discuss the feasibility for development of these inducers as possible drugs to prevent or treat infections.
The epithelium that covers the conducting airways and alveoli is a primary target for inhaled toxic substances, and therefore a focus in inhalation toxicology. The increasing concern about the use of ...animal models has stimulated the development of in vitro cell culture models for analysis of the biological effects of inhaled toxicants. However, the validity of the current in vitro models and their acceptance by regulatory authorities as an alternative to animal models is a reason for concern, and requires a critical review. In this review, focused on human lung epithelial cell cultures as a model for inhalation toxicology, we discuss the choice of cells for these models, the cell culture system used, the method of exposure as well as the various read-outs to assess the cellular response. We argue that rapid developments in the 3D culture of primary epithelial cells, the use of induced pluripotent stem cells for generation of lung epithelial cells and the development of organ-on-a-chip technology are among the important developments that will allow significant advances in this field. Furthermore, we discuss the various routes of application of inhaled toxicants by air-liquid interface models as well as the vast array of read-outs that may provide essential information. We conclude that close collaboration between researchers from various disciplines is essential for development of valid methods that are suitable for replacement of animal studies for inhalation toxicology.
The lung epithelium has long been overlooked as a key player in tuberculosis disease. In addition to acting as a direct barrier to
(Mtb), epithelial cells (EC) of the airways and alveoli act as first ...responders during Mtb infections; they directly sense and respond to Mtb by producing mediators such as cytokines, chemokines and antimicrobials. Interactions of EC with innate and adaptive immune cells further shape the immune response against Mtb. These three essential components, epithelium, immune cells and Mtb, are rarely studied in conjunction, owing in part to difficulties in coculturing them. Recent advances in cell culture technologies offer the opportunity to model the lung microenvironment more closely. Herein, we discuss the interplay between lung EC, immune cells and Mtb and argue that modelling these interactions is of key importance to unravel early events during Mtb infection.
Regulation of bacterial phagocytosis of human macrophages by antimicrobial peptide LL‐37, and its potential mechanisms.
LL‐37/hCAP‐18 is the only human member of the cathelicidin family and plays an ...important role in killing various pathogens, as well as in immune modulation. In this study, we investigated the effect of LL‐37 on bacterial phagocytosis by macrophages and demonstrate that LL‐37 enhances phagocytosis of IgG‐opsonized Gram‐negative and Gram‐positive bacteria in a dose‐ and time‐dependent manner by dTHP‐1 cells. In addition, LL‐37 enhanced phagocytosis of nonopsonized Escherichia coli by human macrophages. Consistently, LL‐37 elevated the expression of FcγRs on macrophages but not the complement receptors CD11b and ‐c. Further studies revealed that the expression of TLR4 and CD14 is also increased on LL‐37‐treated macrophages. Several lines of evidence indicated that the FPR2/ALX receptor mediated LL‐37‐induced phagocytosis. However, TLR4 signaling was also coupled to the phagocytic response, as a specific TLR4 antibody significantly suppressed phagocytosis of IgG‐opsonized E. coli and nonopsonized E. coli by dTHP‐1 cells. Finally, macrophages from Cnlp−/− mice exhibited diminished bacterial phagocytosis compared with macrophages from their WT littermates. In conclusion, we demonstrate a novel, immune‐modulatory mechanism of LL‐37, which may contribute to bacterial clearance.
Cationic host defence peptides (CHDPs), also known as antimicrobial peptides, exhibit a wide range of activities contributing to immune responses and resolution of infections. CHDPs are expressed ...across diverse species, are generally amphipathic with less than 50 amino acids in length, and differ significantly in sequence and structure. This chapter focuses on the role of these peptides in immunity. CHDPs are known to function in both innate and adaptive immune responses. These peptides exert both pro- and anti-inflammatory properties, which are likely context dependent based on cell and tissue type, concentration of the peptides, and its interaction with other factors in the microenvironment. Furthermore, the crosstalk between CHDPs and the microbiome and how this may influence mucosal immunity is a rapidly emerging field of research. Overall, the immunomodulatory functions of CHDPs play an important role in the control of infections, regulation of inflammation, and maintaining immune homeostasis. It is thus not surprising that dysregulation of expression of CHDPs is implicated in the susceptibility, pathology, and progression of various diseases. In this chapter, we summarize the immunomodulatory functions of CHDPs, its clinical relevance, and the translational opportunities that these peptides provide for the development of new therapies.
RATIONALE:The leukocyte response in acute inflammation is characterized by an initial recruitment of neutrophils preceding a second wave of monocytes. Neutrophil-derived granule proteins were ...suggested to hold an important role in this cellular switch. The exact mechanisms by which neutrophils mediate these processes are only partially understood.
OBJECTIVE:To investigate the role of neutrophils and their granule contents in the adhesion of monocyte subpopulations in acute inflammation.
METHODS AND RESULTS:Here, we show that neutrophil-derived cathelicidins (humanLL37, mouseCRAMP) induce adhesion of classical monocytes but not of nonclassical monocytes in the mouse cremaster muscle and in in vitro flow chamber assays. CRAMP is released from emigrated neutrophils and then transported across the endothelium, where it is presented to rolling leukocytes. Endothelial-bound cathelicidin activates formyl-peptide receptor 2 on classical monocytes, resulting in monocytic β1- and β2-integrin conformational change toward an extended, active conformation that allows for adhesion to their respective ligands, vascular cell adhesion molecule 1 and intercellular adhesion molecule 1.
CONCLUSIONS:These data elucidate a novel mechanism of neutrophil-mediated monocyte recruitment, which could be targeted in conditions where recruitment of classical monocytes plays an unfavorable role.
It is currently unknown how cigarette smoke-induced airway remodelling affects highly expressed respiratory epithelial defence proteins and thereby mucosal host defence.Localisation of a selected set ...of highly expressed respiratory epithelial host defence proteins was assessed in well-differentiated primary bronchial epithelial cell (PBEC) cultures. Next, PBEC were cultured at the air-liquid interface, and during differentiation for 2-3 weeks exposed daily to whole cigarette smoke. Gene expression, protein levels and epithelial cell markers were subsequently assessed. In addition, functional activities and persistence of the cigarette smoke-induced effects upon cessation were determined.Expression of the polymeric immunoglobulin receptor, secretory leukocyte protease inhibitor and long and short PLUNC (palate, lung and nasal epithelium clone protein) was restricted to luminal cells and exposure of differentiating PBECs to cigarette smoke resulted in a selective reduction of the expression of these luminal cell-restricted respiratory host defence proteins compared to controls. This reduced expression was a consequence of cigarette smoke-impaired end-stage differentiation of epithelial cells, and accompanied by a significant decreased transepithelial transport of IgA and bacterial killing.These findings shed new light on the importance of airway epithelial cell differentiation in respiratory host defence and could provide an additional explanation for the increased susceptibility of smokers and patients with chronic obstructive pulmonary disease to respiratory infections.
Abstract
Background
Acute exacerbations of chronic inflammatory lung diseases, such as chronic obstructive pulmonary disease (COPD), are frequently associated with rhinovirus (RV) infections. Despite ...these associations, the pathogenesis of virus-induced exacerbations is incompletely understood. We aimed to investigate effects of cigarette smoke (CS), a primary risk factor for COPD, on RV infection in airway epithelium and identify novel mechanisms related to these effects.
Methods
Primary bronchial epithelial cells (PBEC) from COPD patients and controls were differentiated by culture at the air–liquid interface (ALI) and exposed to CS and RV-A16. Bulk RNA sequencing was performed using samples collected at 6 and 24 h post infection (hpi), and viral load, mediator and
l
-lactate levels were measured at 6, 24 and 48hpi. To further delineate the effect of CS on RV-A16 infection, we performed growth differentiation factor 15 (GDF15) knockdown,
l
-lactate and interferon pre-treatment in ALI-PBEC. We performed deconvolution analysis to predict changes in the cell composition of ALI-PBEC after the various exposures. Finally, we compared transcriptional responses of ALI-PBEC to those in nasal epithelium after human RV-A16 challenge.
Results
CS exposure impaired antiviral responses at 6hpi and increased viral replication at 24 and 48hpi in ALI-PBEC. At 24hpi, CS exposure enhanced expression of RV-A16-induced epithelial interferons, inflammation-related genes and CXCL8. CS exposure increased expression of oxidative stress-related genes, of GDF15, and decreased mitochondrial membrane potential.
GDF15
knockdown experiments suggested involvement of this pathway in the CS-induced increase in viral replication. Expression of glycolysis-related genes and
l
-lactate production were increased by CS exposure, and was demonstrated to contribute to higher viral replication. No major differences were demonstrated between COPD and non-COPD-derived cultures. However, cellular deconvolution analysis predicted higher secretory cells in COPD-derived cultures at baseline.
Conclusion
Altogether, our findings demonstrate that CS exposure leads to higher viral infection in human bronchial epithelium by altering not only interferon responses, but likely also through a switch to glycolysis, and via GDF15-related pathways.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Exacerbation in asthma is associated with decreased expression of specific host defence peptides (HDPs) in the lungs. We examined the effects of a synthetic derivative of HDP, innate defence ...regulator (IDR) peptide IDR-1002, in house dust mite (HDM)-challenged murine model of asthma, in interleukin (IL)-33-challenged mice and in human primary bronchial epithelial cells (PBECs).
IDR-1002 (6 mg/kg per mouse) was administered (subcutaneously) in HDM-challenged and/or IL-33-challenged BALB/c mice. Lung function analysis was performed with increasing dose of methacholine by
Vent small animal ventilator, cell differentials in bronchoalveolar lavage performed by modified Wright-Giemsa staining, and cytokines monitored by MesoScale Discovery assay and ELISA. PBECs stimulated with tumour necrosis factor alpha (TNF-α) and interferon gamma (IFN-γ), with or without IDR-1002, were analysed by western blots.
IDR-1002 blunted HDM challenge-induced airway hyper-responsiveness (AHR), and lung leucocyte accumulation including that of eosinophils and neutrophils, in HDM-challenged mice. Concomitantly, IDR-1002 suppressed HDM-induced IL-33 in the lungs. IFN-γ/TNF-α-induced IL-33 production was abrogated by IDR-1002 in PBECs. Administration of IL-33 in HDM-challenged mice, or challenge with IL-33 alone, mitigated the ability of IDR-1002 to control leucocyte accumulation in the lungs, suggesting that the suppression of IL-33 is essential for the anti-inflammatory activity of IDR-1002. In contrast, the peptide significantly reduced either HDM, IL-33 or HDM+IL-33 co-challenge-induced AHR in vivo.
This study demonstrates that an immunomodulatory IDR peptide controls the pathophysiology of asthma in a murine model. As IL-33 is implicated in steroid-refractory severe asthma, our findings on the effects of IDR-1002 may contribute to the development of novel therapies for steroid-refractory severe asthma.
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